It just looks like your scaling/conversion if off.
The Spike user manual documents the equations used to convert the file contents to scaled I/Q values, if you haven’t seen this already.
Have you stepped through your code and verified scale factor is correct?
Have you tried verifying your conversion works for fixed values? You could force 1+0i (SHRT_MAX,0) and fixed scalings to verify the conversion works properly.
That should fix the AMvTime plot. Our I/Q plot is in mV, so there would need to be another conversion if you wanted those units. Right now you are simply plotting I/Q straight from the device it appears.
I’m not sure whats happening with the FM. Maybe really small values create this? zero values? It doesn’t look like a phase discontinuity. Maybe phase wrapping like Justin said?
Regards